Bandwidth Statistics

Monitoring how much bandwidth is being used is a common feature of many routers. The same thing can be done on an OpenBSD box quite easily. We'll install the "vnstat" daemon and tell it to monitor each interface.

# pkg_add vnstat
# vnstat -u -i em0
# vnstat -u -i em1
# vnstat -u -i em2
# vnstat -u -i em3
# chown _vnstat /var/db/vnstat/*

If you only care about WAN traffic statistics, just enable it for the egress interface, which is em0 in my case. Next, make any changes you want to the configuration file:

# vi /etc/vnstat.conf

I like to make things a bit more human-readable:

--- vnstat.conf     Sat May  2 21:15:35 2015
+++ vnstat.conf     Sat May  2 21:13:32 2015
@@ -28,7 +28,7 @@
 # how units are prefixed when traffic is shown
 # 0 = IEC standard prefixes (KiB/MiB/GiB/TiB)
 # 1 = old style binary prefixes (KB/MB/GB/TB)
-UnitMode 0
+UnitMode 1

 # output style
 # 0 = minimal & narrow, 1 = bar column visible
@@ -37,11 +37,11 @@
 OutputStyle 3

 # used rate unit (0 = bytes, 1 = bits)
-RateUnit 1
+RateUnit 0

 # maximum bandwidth (Mbit) for all interfaces, 0 = disable feature
 # (unless interface specific limit is given)
-MaxBandwidth 100
+MaxBandwidth 0

 # interface specific limits
 #  example 8Mbit limit for 'ethnone':

Be sure to add the rc.d script to your startup items, alongside dnscrypt-proxy.

# grep scripts /etc/rc.conf.local

pkg_scripts="dnscrypt_proxy vnstatd"

Finally, start the daemon.

# /etc/rc.d/vnstatd start

Wait a few minutes and it should start collecting data.

# vnstat -i em0

    Database updated: Tue Jun  9 15:41:10 2015

   em0 since 05/02/15

          rx:  334.15 GB      tx:  110.72 GB      total:  444.88 GB

   monthly
                     rx      |     tx      |    total    |   avg. rate
     ------------------------+-------------+-------------+---------------
       May '15     265.71 GB |    53.94 GB |   319.66 GB |    125.14 KB/s
       Jun '15      68.44 GB |    56.78 GB |   125.22 GB |    175.62 KB/s
     ------------------------+-------------+-------------+---------------
     estimated     237.26 GB |   196.85 GB |   434.11 GB |

   daily
                     rx      |     tx      |    total    |   avg. rate
     ------------------------+-------------+-------------+---------------
     yesterday       3.03 GB |     1.43 GB |     4.46 GB |     54.09 KB/s
         today       2.68 GB |   134.89 MB |     2.82 GB |     52.28 KB/s
     ------------------------+-------------+-------------+---------------
     estimated       4.11 GB |      205 MB |     4.31 GB |

That's all there is to it.